There are numerous applications with the need for extremely miniaturized motors that are able to make controlled fine positioning. For example, in consumer products extremely small, low weight, low power consumption and inexpensive motors are typically requested. The motion range is often in the order of millimeters and with an accuracy of micrometers.
In the published international patent application U.S. Pat. No. 6,437,485 B1 an electromechanical actuator based on a double electromechanical element is disclosed. The electromechanical elements have electrical connections at the outer end faces and mechanical supports against a stator at respective outer ends and are interconnected by an electromechanically inactive portion, to which a driving portion is attached. By supplying well-defined voltage signals to multimorphs, bimorphs or monomorphs of each electromechanical element, the driving portion is moved in two dimensions for transferring a motion to a body. The basic concept proved to be very useful. However, in order to optimize the dynamic behavior of the electromechanical elements for different applications, very high assembling precision, time-consuming empirical tests, high sensitivity to external conditions and/or precautions to prevent fatigue may be necessary. In particular, the electrical and mechanical connects were difficult to accomplish in a controlled manner. During the soldering process, there are for instance several geometrical parameters that have to be well controlled which is difficult to obtain in an automated process. Since the vibrating drive element will have substantial vibration amplitude at the end face, the electrical and mechanical connects will also be exposed to large mechanical stresses, which is highly undesirable. With the flexible printed circuit board attached to the end faces, the damping of the vibrations will also increase and the efficiency will therefore be reduced. In a general case, the relations between more or less controllable parameters are very complicated.
Many of the products envisioned for this type of electromechanical motor are extremely price sensitive, and if the tolerances in manufacturing are too narrow, there will be a reduction in yield and hence a higher cost. Prior-art electromechanical motors are generally not particularly well suited for cost-efficient mass production.